1. Field of the Invention
The present invention relates generally to a trench type power transistor device and a manufacturing method thereof, and more particularly, to a trench type power transistor device with super junction and a manufacturing method thereof.
2. Description of the Prior Art
In power transistor devices, the ON resistance (RDS(on)) between the drain and the source is proportional to the power consumption of the device, so an effective way to reduce the power consumption of the power transistor device is to lower the RDS(on). In power transistor devices, the resistance provided by the epitaxial layer used for withstanding high voltage is the main contribution to the RDS(on). However, another function of the epitaxial layer is to withstand the high voltage. Although increasing the doping concentration of the conductive material in the epitaxial layer can reduce the resistance, the breakdown voltage of the epitaxial layer will also be lowered, and the capacity of the power transistor device to withstand high voltages is degraded.
In order to maintain or increase the voltage withstanding ability of the power transistor device and lower the resistance of epitaxial layer, a power transistor device with a super junction with high voltage withstanding ability and low ON resistance has been developed in the industry. In conventional power transistor devices, P-type epitaxial layers and N-type epitaxial layers are formed alternatively on the substrate along a horizontal direction, so that the P-type epitaxial layers and N-type epitaxial layers may constitute a plurality of P-N junctions parallel to each other and perpendicular to the surface of the substrate. A conventional manufacturing method of the power transistor device uses an etching process to form a plurality of deep trenches in the N-type epitaxial layer, and a P-type epitaxial layer is then filled into each deep trench. However, the aspect ratio of the deep trench has a predetermined value, and the aspect ratio of the deep trench made by the etching process has its process limitation. Also, the P-type epitaxial layer can't completely fill up the deep trench, and voids are easily formed in the P-type epitaxial layer, so that the super junction has defects.
In view of this matter, the main objective of the industry in the current stage is to provide a novel trench type power transistor device and a manufacturing method thereof to prevent the formed super junction from having defects.